Problem: Solve for $n$ : $n - 12 = -24$
Solution: Add $12$ to both sides: $ \begin{eqnarray} \\ n - 12 &=& -24 \\ \\ {+12} && {+12} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-12 + n} &\hphantom{=}& \hphantom{-24} \\ n &=& -24 {+ 12} \\ \end{eqnarray} $ Simplify. $ n = -12$